Isolation structures are formed in an integrated circuit for the purpose of preventing carriers from penetrating through the substrate to neighboring components. For example, in standard CMOS transistor processing, an isolation trench is etched into a semiconductor substrate and a liner is formed in the trench by oxidation. The liner oxidation is carried out for a number of reasons including rounding of the trench corner to provide better breakdown characteristics, formation of a high quality dielectric layer, creating a trench structure which is easy to fill, passivation of damage from the RIE (reactive ion etching), minimization of effects of contamination and improvement of the electrical characteristics of the trench isolation.
Historically, standard batch furnace processing has been used to carry out the liner oxidation. Such processing typically provides some rounding of the corners of the liner as well as providing a relatively high quality oxide on the sidewalls of the trench. However, the oxide that is grown by standard batch furnace processing is not especially conformal. In particular, the oxide typically forms in a bread loaf like configuration. This in turn renders the trench that remains after growing of the sidewalls somewhat challenging to fill by currently available deposition processing. Furthermore, although some rounding of the corners does occur using standard batch furnace processing, the rounding is not as much as desired for satisfying the needs of current state of the art devices.
The present invention provides a method for forming a liner in a trench that exhibits enhanced rounded corners in the top and bottom of the trench as well as exhibiting a conformal structure. In particular, the method of the present invention comprises forming a liner in a trench wherein the liner has rounded corners in the top and bottom of the trench and which comprises forming the liner by rapid thermal oxidation.
In addition, the present invention relates to lined trenches formed by the above-disclosed method. The liners achieved by the present invention exhibit uniform growth along the sidewalls of the trench and exhibit reduced stress.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive.